Laser-Guided Technology Could Lead To Smaller, More Affordable Particle Accelerators

September 28, 2013

Image Caption: The nanoscale patterns of SLAC and Stanford's accelerator on a chip gleam in rainbow colors prior to being assembled and cut into their final forms. Credit: Matt Beardsley/SLAC

redOrbit Staff & Wire Reports – Your Universe Online

A new technique used by researchers from the US Department of Energy’s SLAC National Accelerator Laboratory and Stanford University could dramatically reduce the size of particle accelerators.

The scientists used a laser to accelerate electrons at 10 times that of conventional technology, doing so in a nanostructured glass chip smaller than a grain of rice. Their breakthrough could result in new medical and scientific devices that are smaller and less expensive than those currently available.

“We still have a number of challenges before this technology becomes practical for real-world use, but eventually it would substantially reduce the size and cost of future high-energy particle colliders for exploring the world of fundamental particles and forces,” SLAC physicist Joel England, who was in charge of the experiments, explained in a statement.

Since their method uses commercially available lasers and inexpensive, mass-production techniques, England and his colleagues believe that it could lead the way to the next generation of smaller accelerators.

He added that their research, which is fully explained in Friday’s edition of the journal Nature, “could also help enable compact accelerators and X-ray devices for security scanning, medical therapy and imaging, and research in biology and materials science.”

Their so-called “accelerator on a chip” could have the same accelerating power as the SLAC’s two-mile-long linear accelerator in just 100 feet, when it reaches its full potential. Furthermore, England and his colleagues believe that the smaller accelerator is capable of delivering a million more electron pulses per second.

The study authors report that their initial demonstration was able to achieve an acceleration gradient – the amount of energy gained per unit of length – of 300 million electronvolts per meter. Essentially, that means that the smaller “accelerator on a chip” can produce approximately 10 times more acceleration than its larger counterpart.

According to principal investigator Robert Byer, a professor in the Stanford Department of Applied Physics, the scientists are ultimately hoping that their miniature accelerator will be able to produce one-billion electronvolts per meter – just three times what it achieved in the team’s very first test.

The researchers explained that current accelerators require microwaves in order to boost the energy of electrons, and that experts have been searching for more economical alternatives. They hope that their new method, which utilizes extremely fast lasers to drive the accelerator, could be the highly sought-after solution.

The particle acceleration process typically takes place in two parts. First, the particles are boosted close to the speed of light. Then they undergo additional acceleration – but this stage requires that their speed not be increased, and according to the researchers, this is the difficult part.

In their experiments, Byer, England and their associates used a conventional accelerator to complete the first part of the process. Then the excited electrons are focused into a one-half micron high channel inside of a fused, one millimeter long silica glass chip. That channel had been designed with precisely-spaced nanoscale ridges, and infrared laser light shining on the pattern created by those ridges generated electrical fields that interacted with the particles and helped boost their energy.

The researchers admit that they will have to find a more compact way to get the particles to near-light speed before they enter the device before their device can become a fully operational tabletop accelerator. Once they do, however, the technology could be used for X-ray free-electron lasers, portable X-ray sources used to help treat soldiers injured in combat, and less expensive medical imaging for hospitals and laboratories.

Image 2 (below): The key to the accelerator chips is tiny, precisely spaced ridges, which cause the iridescence seen in this close-up photo. Credit: Brad Plummer/SLAC